This invention relates to a keyboard musical instrument and, more particularly, to a keyboard musical instrument equipped with hammers such as, for example, an automatic player piano and a silent piano and a hammer sensor used therein.
The automatic player piano is a composite keyboard musical instrument fabricated on the basis of an acoustic piano. An array of solenoid-operated key actuators and an array of key sensors are provided in association with the keyboard, and an electronic controlling system is connected to the array of solenoid-operated key actuators and the array of key sensors. While a pianist is playing a tune on the keyboard, the black and white keys are selectively depressed by the pianist, and the associated key sensors report the key motion to the electronic controlling system. The electronic controlling system specifies the depressed black/white keys and the released black/white keys, and determines the lapse of time at which the black/white keys are depressed and released. Moreover, the electronic controlling system calculates the key velocity. These pieces of music data information are stored in a set of music data codes for playback.
When a user instructs the electronic controlling system to reproduce the performance, the electronic controlling system reads out the pieces of music data information. The electronic controlling system supplies driving signals to the solenoid-operated key actuators at the same timing as in the original performance, and the solenoid- operated key actuators move the associated black/white keys without any fingering on the keyboard. Thus, the automatic player piano records the original performance, and reproduces the original performance without any fingering on the keyboard.
The silent piano is another composite keyboard musical instrument. An array of key sensors is provided in association with the keyboard, and an electronic tone generating system is connected to the array of key sensors. A hammer stopper is changeable between a free position and a blocking position. When the hammer stopper is changed to the free position, the hammer stopper is moved out of the trajectories of the hammers. The pianist selectively strikes the music strings with the hammers through the fingering on the keyboard, and the acoustic piano tones are generated from the vibrating music strings. If the pianist changes the hammer stopper to the blocking position, the hammer stopper is moved into the trajectories of the hammers. Even though the pianist fingers a tune on the keyboard, the hammers rebound on the hammer stopper before striking the music strings, and any acoustic piano tone is not generated from the music strings. However, the key sensors monitor the associated black/white keys, and report the key motion to the electronic tone generating system. The electronic tone generating system specifies the depressed black/white keys and the released black/white keys, and determines the key velocity. The electronic tone generating system produces an electric signal representative of the tones to be generated, and electronic tones are produced by a sound system.
Thus, the key sensors are indispensable in both automatic player and silent pianos. When a pianist simply depresses the black/white keys from the rest positions to the end positions, the key sensors exactly report the key motion to the electronic controlling/electronic tone generating system, and the reproduced tone/electronic tone is fairly equivalent to the original tone, because the associated hammer is driven for rotation at a hammer velocity proportional to the key velocity. However, the performance is usually not constituted by the simple key motion. A black/white key may be repeatedly depressed by the pianist, and another black/white key may return on the way to the end position. In this situation, the key motion does not give rise to the hammer motion at a hammer velocity proportional to the key motion. As a result, the reproduced tone/electronic tone is generated at loudness different from the original piano tone/the piano tone to be generated. Thus, the key sensors hardly respond to the complicated key motion.
In order to exactly determine the hammer motion, it has been proposed directly to detect the hammer motion. An array of hammer sensors is installed inside the piano case. The hammer sensors directly monitor the associated hammers, and report the current positions of the associated hammers. With the pieces of positional information, the electronic controlling system/electronic tone generating system exactly determines the hammer motion, and stores the pieces of music data information in the music data codes.
There are several kinds of hammer sensors which have been already known. The first kind of hammer sensor is a combination of a shutter plate and a photo-coupler. The shutter plate is formed with a window. Otherwise, the photo-coupler produces plural light beams. The shutter plate is assumed to have the window. The shutter plate is fixed to the hammer shank, and, accordingly, is movable together with the hammer assembly. The photo-coupler is, by way of example, supported by the action brackets, and produces the light beam across the trajectory of the shutter plate. When the associated black and white key is depressed, the action mechanism drives the hammer assembly for rotation, and the shutter plate is moved along the trajectory. When the shutter plate reaches the light beam, the shutter plate intercepts the light beam. The shutter plate continuously intercepting the light beam until the window reaches. The shutter plate permits the light beam to pass the window, and intercepts the light beam, again. The electronic controlling system/electronic tone generating system calculates the hammer velocity on the basis of the lapse of time between the interception at the front and the passage through the window. The shutter plate is appropriately designed so that the electronic controlling system/electronic tone generating system determines the timing at which the hammer strikes the string.
The second kind of the hammer sensor is shown in FIG. 1, and is a combination of a reflecting photo-coupler 500 and a reflecting sheet 502. The reflecting photo-coupler 500 is fixed to a stationary bracket 500, and radiates a light beam toward a hammer assembly 503. On the other hand, the reflecting sheet 502 is attached to the hammer shank 504, and is moved together with hammer assembly 503 along the trajectory of the hammer shank 504. The light beam is always reflected on the reflecting sheet 502, and returns to the reflecting photo-coupler 500. The amount of reflected light is varied depending upon the current hammer position, and the reflecting photo-coupler 500 reports the amount of reflected light to the electronic controlling system/electronic tone generating system. The electronic controlling system/electronic tone generating system determines the current hammer position, and calculates the hammer velocity. The electronic controlling system/electronic tone generating system determines the time at which the hammer strikes the music string 505 when the amount of reflected light reaches a predetermined value.
The third kind of hammer sensor is a combination of a Hall-effect element and a permanent magnet piece. The reflecting photo-coupler 500 is replaced with the Hall-effect element, and the piece of permanent magnet piece is attached to the hammer shank 504. The magnetic field strength is varied together with the distance between the Hall-effect element and the permanent magnet piece, and the Hall-effect element generates the electric current in the magnetic field created by the permanent magnetic piece. The amount of current is representative of the magnetic field strength and, accordingly, the distance between the Hall-effect element and the permanent magnetic piece. The electronic controlling system/electronic tone generating system determines the current hammer position on the basis of the amount of electric current, and calculates the hammer velocity. When the amount of electric current reaches a predetermined value, the electronic controlling system/electronic tone generating system decides that the time to strike the music string comes. Thus, these kinds of hammer sensors cooperate with the electronic controlling system/electronic tone generating system, and assist the electronic controlling system/electronic tone generating system in the recording and generating the pieces of music data information representative of the performance on the keyboard. However, the following problems are encountered in those kinds of hammer sensors.
A problem inherent in the first kind of the hammer sensor is that the array of hammer sensors is liable to be deviated from the appropriate position. The electronic controlling system/electronic tone generating system decides the time to strike the music string on the basis of the timing at which the light beam passes the window, again. This means that the electronic controlling system/electronic tone generating system decides the time to strike the music string on the assumption that the photo-coupler and the shutter plate are appropriately positioned at the target points. If the photo-coupler or the shutter plate is deviated from the target position, the electronic controlling system/electronic tone generating system can not exactly decides the time to strike the music string. Careful work is required for the first kind of hammer sensor, and the tuning work is periodically to be done.
Another problem inherent in the first kind of hammer sensor is the narrow detectable range. The detectable range is equivalent to the distance between the front of the shutter plate and the window formed therein, and the trajectory of the hammer assembly is much longer than the detectable range. However, the photo-coupler does not change the amount of photo-current outside the detectable range. The electronic controlling system/electronic tone generating system can not obtain any piece of positional information outside the detectable range.
A problem inherent in the second kind of hammer sensor is serious noise component riding on the electric signal representative of the current hammer position. If the second kind of hammer sensor was installed in the ideal environment where the background illuminance was constant, the second kind of hammer sensor would generate the electric signal exactly representative of the current hammer position. However, the natural light and/or room light is incident on the photo-coupler. Unfortunately, the intensity of the natural light/room light is variable depending upon the season and the position of the composite keyboard musical instrument. This means that the manufacturer can not predict the background illuminance. For this reason, the noise component is serious, and makes the electronic controlling system/electronic tone generating system mistakenly decide the current hammer position and the time to strike the music string.
A problem inherent in the third kind of hammer sensor is also serious noise component. This is because of the fact that the Hall-effect element is placed in the magnetic field created by the adjacent permanent magnetic pieces as well as in the magnetic field created by the associated permanent magnetic piece. The hammer assemblies are independently driven for rotation, and the magnetic field strength at each Hall-effect element is varied together with not only the current hammer position of the associated hammer assembly but also the current hammer positions of the adjacent hammer assemblies. The magnetic influence of the adjacent permanent magnetic pieces is causative of the noise component.
Still another problem inherent in the second and third kinds of hammer sensors is an error component due to an approximation. The output voltage of the photo-coupler/Hall-effect element is varied from the rest position to the end position as indicated by non-linear plots PL1 (see FIG. 2A). The electronic controlling system/electronic tone generating system approximates the non-linear plots PL1 to linear plots PL2 (see FIG. 2B), and determines the current hammer position on the basis of the linear plots PL2. The difference between the non-linear plots PL1 and the linear plots PL2 is introduced into the pieces of positional data information. The electronic controlling system/electronic tone generating system produces the pieces of music data information on the basis of the pieces of positional data information, and the error component is left in the pieces of music data information.
It is therefore an important object of the present invention to provide a keyboard musical instrument, which exactly produces tones.
It is also an important object of the present invention to provide a hammer sensor, which has a wide detectable range and good reliability in producing an output signal exactly representing current hammer position.
In accordance with one aspect of the present invention, there is provided a keyboard musical instrument for producing tones comprising plural keys independently movable between respective rest positions to respective end positions, plural action mechanisms respectively connected to the plural keys so that moving keys actuate the associated action mechanisms, plural hammers respectively associated with the plural action mechanisms, and driven for rotation by the associated action mechanisms, and a music data generating system including plural hammer sensors respectively monitoring the plural hammers for detecting a physical quantity of the plural hammers respectively rotatable on virtual planes with respect to a member, each of the plural hammer sensors having a photo radiating element stationary with respect to the member and radiating a light beam along an optical path at least a part of which extends in a direction crossing the virtual plane of the associated hammer, a photo receiving element stationary with respect to the member and provided on the optical path for producing a hammer signal representative of the amount of incident light and a converter rotatable together with the associated hammer and radiated with the light beam for converting a variation of the physical quantity to a variation of the amount of incident light and a data processing sub-system connected to the plural hammer sensors for receiving the hammer signals and analyzing a hammer motion represented by the variation of the amount of incident light for each of the plural hammers so as to produce an audio signal representative of the tone to be produced through the hammer motion.
In accordance with another aspect of the present invention, there is provided a hammer sensor for detecting a physical quantity of a hammer rotatable on a virtual plane with respect to a member comprising a photo radiating element stationary with respect to the member and radiating a light beam along an optical path at least a part of which extends in a direction crossing the virtual plane, a photo receiving element stationary with respect to the member and provided on the optical path for producing an electric signal representative of the amount of an incident light, and a converter rotatable together with the hammer, and radiated with the light beam for converting a variation of the physical quantity to a variation of the amount of incident light.